As wireless networks evolve and grow, there are ongoing challenges in providing high-quality service to increasing numbers of wireless devices in various coverage areas of a wireless network. Multiple-input and multiple-output (MIMO) is used to multiply the capacity of a radio interface using multiple transmit and receive antennas. Different types of MIMO transmission modes may be used to communicate with the wireless devices attached to an access node. One such type of transmission mode utilizes transmit diversity, which includes sending redundant (i.e. identical) information across plural transmit antennas to improve the quality in the received signal. This transmission mode exploits the diversity of possible transmission paths between a transmitter and a receiver, thereby improving reliability and decreasing the probability of error. Another transmission mode uses spatial multiplexing, which includes transmitting an independent data stream on each antenna for effectively sending multiple data streams in parallel. This mode enables transmission of data generally at a higher rate, but typically less reliably than with transmit diversity. Transmit diversity is well suited for wireless devices (and applications running thereon) requiring extremely high reliability such as at an edge of a coverage area, whereas wireless devices (and applications running thereon) that can smoothly handle losses or are close to an access node benefit from spatial multiplexing. However, existing access nodes are limited in their ability to handle both transmission modes to their highest potential, particularly when the arrangement and spacing of physical antennae are not optimized.
Overview
Exemplary embodiments described herein include systems, methods, and processing nodes for communicating via a plurality of antennae. In one exemplary embodiment, a method for communicating via a plurality of antennae includes transmitting different data streams from each of a first antenna and a second antenna in a first transmission mode, and transmitting identical data streams from a third antenna and one of the first and second antennae in a second transmission mode. The first and second antennae are horizontally stacked relative to each other and the third antenna is vertically stacked relative to both the first and second antennae.
In another exemplary embodiment, a system for communicating via a plurality of antennae includes a first antenna, a second antenna positioned horizontally adjacent the first antenna, a third antenna positioned vertically adjacent both the first and second antennae, and a processing node communicatively coupled to each of the first, second, and third antennae. The processing node is configured to determine a transmission mode from among a spatial multiplexing mode using the first and second antennae and a transmit diversity mode using the third antenna and one of the first and second antennae.
In yet another exemplary embodiment, a processing node for communicating via a plurality of antennae is configured to perform operations comprising utilizing a first pair of antennae in a spatial multiplexing transmission mode, wherein the first pair of antennae is horizontally-stacked and, upon a signal condition meeting a threshold, utilizing a second pair of antennae in a transmit diversity transmission mode, wherein the second pair of antennae is vertically-stacked. Both first and second pairs have one antenna in common.